Hi. You should know that the menstrual cycle varies from person to person based on the hormonal level, body built, nutrition etc.so just a few days of variation from your regural periods is acceptable. Apart from this there are many causes which results in delayed period like uterine scarring due to some procedures,uterine abnormality, fibroid in uterus or endometriosis,certain medications, hormonal imbalance like thyroid disorders will effect menstrual cycle or pituitary disorders can also affect menstrual cycle or it might be PCOS. Stopping medications causing delayed periods will itself improve your condition.hyperthyroidism or hypothyroidism treatment will help in bringing back the menstrual cycle to normalcy to some extent.If its a PCOS(polycystic ovarian syndrome) you may also experience pimples, weight gain, excessive hair growth on your body,sometimes even depression will be there. If you are still concerned kindly consult a gynecologist for further management.